Updated resource for java performance tuning

Question

Can anyone recommend a web site that includes up to date performance tips for Java? Most of the sites I have found seem to be old and I guess the newer versions (1.5 - 1.7) may have obsoleted some recommendations.

Edit:

I'm mostly concerned with reducing memory usage/garbage collection and making sure that simple methods can be inlined if necessary.

The code involves processing large amounts of data in threads using lots of small objects. Some objects are created for each data item, while others live longer. These objects usually implement an Interface or extending an abstract class.

Answer 1

Update: For me, the reference document to tune a Sun virtual machine is Java SE 6 HotSpot^TM Virtual Machine Garbage Collection Tuning (that will also give you a methodology).

As mentioned in a comment, the ergonomics feature does a pretty good job at tuning a modern JVM and should be tried first before to test more detailed controls.

If you don't get satisfying results, set the max Heap size and start to play with the generation sizes and more precisely the Young Generation. From the FAQ about Garbage Collection in the Hotspot^TM Java^TM Virtual Machine:

The young generation should be sized large enough so that short-lived objects have a chance to die before the next young generation collection. This is a tradeoff since a larger young generation will allow more time for objects to die but may also take longer to collect. Experiment with the size of the young generation to optimize the young generation collection time or the application throughput.

I'd follow the suggested approach:

The rules of thumb for server applications are:

• First decide the maximum heap size you can afford to give the virtual machine. Then plot your performance metric against young generation sizes to find the best setting.
  • Note that the maximum heap size should always be smaller than the amount of memory installed on the machine, to avoid excessive page faults and thrashing.
• If the total heap size is fixed, increasing the young generation size requires reducing the tenured generation size. Keep the tenured generation large enough to hold all the live data used by the application at any given time, plus some amount of slack space (10-20% or more).
• Subject to the above constraint on the tenured generation:
  • Grant plenty of memory to the young generation.
  • Increase the young generation size as you increase the number of processors, since allocation can be parallelized.

Then, if the application does still not achieve the desired performance, start with a different collector (see Selecting a Collector).

Unless your application has rather strict pause time requirements, first run your application and allow the VM to select a collector. If necessary, adjust the heap size to improve performance. If the performance still does not meet your goals, then use the following guidelines as a starting point for selecting a collector.

1. If the application has a small data set (up to approximately 100MB), then
   • select the serial collector with -XX:+UseSerialGC.
2. If the application will be run on a single processor and there are no pause time requirements, then
   • let the VM select the collector, or
   • select the serial collector with -XX:+UseSerialGC.
3. If (a) peak application performance is the first priority and (b) there are no pause time requirements or pauses of one second or longer are acceptable, then
   • let the VM select the collector, or
   • select the parallel collector with -XX:+UseParallelGC and (optionally) enable parallel compaction with -XX:+UseParallelOldGC.
4. If response time is more important than overall throughput and garbage collection pauses must be kept shorter than approximately one second, then
   • select the concurrent collector with -XX:+UseConcMarkSweepGC. If only one or two processors are available, consider using incremental mode, described below.

Actually, just read the whole document carefully (and be sure to understand the implications of a bad decision :) And don't forget:

If you cannot measure it, you cannot improve it. --Lord Kelvin

References

• Java SE 6 HotSpot^TM Virtual Machine Garbage Collection Tuning
• Java SE 6 Performance White Paper

Below my initial answer that some readers might still find interesting:

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Java Performance Tuning is a well known reference for Java performance and still updated. You might also want to check the blog of the Kirk Pepperdine (which is actually a contributor of the previous site).